1. Field of the Invention
The present invention relates to a semiconductor device and, more particularly, to a semiconductor device with a ball grilled array (BGA) substrate in which a semiconductor chip is packaged.
2. Description of the Related Art
There has lately been an increasing demand for semiconductor devices used in mission-critical communication equipment and high-end computers to be faster and to have higher performance. To meet the demand, semiconductor chips and semiconductor devices in which semiconductor chips are packaged have to be reduced in size. One of miniaturization solutions is BGA packaging.
Techniques that revolve around bonding structures for bonding a BGA package and a circuit substrate are found in, for example, JP 2001-144214 A.
This publication discloses a semiconductor device and its bonding structure which prolong the bonding lifetime by giving metal balls that are on the perimeter a higher tensile strength than that of other metal balls.
Also, an article “1 Gb/s Ether Physical Layer Device Package Development” written by R. Mathew et al. and published in Proceedings of 2006 IEEE ECTC (p 35-40) on May 31, 2006 discloses a semiconductor device structure which accomplishes stable power supply by packaging a chip such that the chip center is decentered from the BGA substrate center.
However, conventional BGA packaging has never given consideration to the positional relation between the edges of a semiconductor chip and balls on a BGA substrate, in particular, the positional relation in a perpendicular direction with respect to the substrate in the process of mounting the semiconductor chip to the BGA substrate. This results in some devices having the edges of a semiconductor chip 1 at positions that align with the centers of solder balls 8 (landing pads 7 where a BGA substrate 9 and the solder balls 8 come into contact, to be exact) in the perpendicular direction of the substrate as shown in FIGS. 9 and 10.
A device assembled without giving consideration to the positional relation in the perpendicular direction between semiconductor chip edges and balls on a BGA substrate as described above has a problem in that, when mounted to another substrate (this is called secondary packaging) and then tested for packaging strength, the solder balls 8 frequently come detached in places where the edges of the semiconductor chip 1 align with the centers of the solder balls 8 on the BGA substrate 9 (the landing pads 7 where the BGA substrate 9 and the solder balls 8 come into contact, to be exact) in the perpendicular direction of the substrate.